The present invention relates to a method for estimating the speech quality in telephony services and, more particularly, to an overall conversational speech quality estimation method and apparatus for estimating the subjective conversational speech quality from measured quantities of physical features of a system under test without conducting subjective evaluation tests for evaluating the actual conversational speech quality in the IP telephony; furthermore, the invention also pertains to a program for implementing the method and a recording medium with the program stored thereon.